Chaetomidium heterotrichum from Venezuela, with a key to species and cladistic analysis of the genus Chaetomidium

Abstract

A species of the genusChaetomidium was isolated from fallen leaves of an unknown tree during a mycofloral survey of materials from the ‘Gran Sabana’ region in Southeastern Venezuela. The species was identified asC. heterotrichum. Identification was based on the perithecium lacking a neck and ostiole, the peridium being composed of textura angularis cells, the perithecium being covered with hairs and setae at the apex, and by 4-spored asci containing uniporate ascospores. The anamorph was intermediate betweenChalara andAcremonium sect.Chaetomioides. This is the first report of this species in Venezuela and only the second timeC. heterotrichum has been found. An illustrated description ofC. heterotrichum and a key to eight recognized species ofChaetomidium, based on morphological characters in the literature, are provided. The results of a cladistic analysis of 12 available morphological characters of the genus revealed two main groups, each based on the two characters ‘ascospore shape’ and ‘peridial wall type’. The ascomatal hairs had little influence on the species grouping. With the exception ofC. heterotrichum, the remaining species ofChaetomidium were monophyletically supported in 73% of the bootstrap replicates.Chaetomidium heterotrichum was the basal ingroup taxon and formed a sister group to the other species in the genus.